Heart failure is characterized by which of the following?

Heart failure is characterized by the heart muscle's inability to pump blood as effectively as it should. This condition can result from various factors such as weakened heart muscle, damage from previous heart attacks, high blood pressure, or diseases affecting the heart's structure. When the heart cannot pump sufficient blood, it leads to inadequate blood flow to meet the body’s needs, causing symptoms like fatigue, shortness of breath, and fluid retention.

The other options do not accurately describe heart failure. Increased blood sugar levels relate to diabetes and not directly to the pumping efficiency of the heart. If the heart pumped blood too effectively, it would not signify heart failure; rather, it would imply good heart function. Narrowing of the arteries, while a significant cardiovascular issue, mainly describes a condition like coronary artery disease, which can lead to heart problems but does not specifically define heart failure itself. Thus, the correct understanding of heart failure directly aligns with the idea that the heart muscle does not function adequately in its pumping capacity.